1. Field of the Invention
The present invention relates generally to an electro-magnetically operated valve whose opening and closing movement is driven by electro-magnetic force and resilient force, and more particularly, it relates to an apparatus for estimating a valve-clearance defined between a valve element and a valve drive element of the electro-magnetically operated valve suitable for being used as intake or exhaust valve of an internal combustion engine. Furthermore, the present invention relates to a valve-operation controller provided with the valve-clearance estimating apparatus and controlling the opening and closing movement of the electro-magnetically operated valve.
2. Description of the Related Art
In a valve drive system of intake and exhaust valves of an internal combustion engine, there has been proposed an electro-magnetic drive system which operates valves by using an electro-magnetic force, instead of the conventional cam-operated valve drive system. The electro-magnetically operated valves do not need any cam-operated drive mechanism for valves, and additionally facilitate the opening and closing timing of the intake and exhaust valves of an internal combustion engine, depending on the operating condition of the internal combustion engine, so that the output of the internal combustion engine may be appreciably increased accompanied by a reduction in the engine fuel consumption.
The electro-magnetically operated valve ordinarily includes a valve drive element made of soft magnetic material, a pair of electro-magnets capable of attracting the valve drive element by electro-magnetic force, and a resilient member or a spring for urging the valve drive element toward its neutral position located between the pair of electro-magnets. The pair of electro-magnets alternatively attract the valve drive element while causing the alternative opening and closing movement of the valve element arranged to move in association with the valve drive element. In this type of electro-magnetically operated valve, when the valve element is secured to the valve drive element so as to be integrally moved, the position of the valve drive element at the time when the valve element is urged to its closing position changes due to thermal extension of a valve stem and abrasion of the valve element and its associated valve seat caused by repeated contacting of the valve element and the valve seat. Thus, such a deficiency of the conventional electro-magnetically operated valve is that the valve element is unable come to the closing position accurately by seating on the associated valve seat.
To overcome this deficiency, there has been proposed a device for moving an electro-magnetically operated valve to its closing position, in which the valve drive element and the valve element of the electro-magnetically operated valve are formed as cooperative separate moving members and a small clearance, which will be herein referred to as a valve-clearance, is provided between the valve drive element moved to its one extreme position for closing the valve element and the valve element located at the completely closing position of the electro-magnetically operated valve.
In order to control the electro-magnetically operated valve to ensure the closing of the valve and reducing the moving speed of the valve at the moment of being seated on the valve seat and thereby sufficiently reducing noise generation at the moment of seating of the valve on the valve seat, it is necessary not only to accurately detect or determine a change in the position of the valve element during the movement thereof but also to determine a certain moment at which the valve is seated on the valve seat. However, it is known that the determination of the position change of the valve element by the use of any position sensor is technically difficult to realize from the viewpoint of a limitation to the mounting of the position sensor on or about the valve element as well as a difficulty in isolating heat, which might transmit from an engine to the position sensor.
On the other hand, although it is possible to arrange a position sensor around the valve drive element in order to detect a change in the position during its movement, detection of position of the valve drive element cannot be effective for accurately detecting or determining the positional change in the moving valve element for the reason that any change in the valve-clearance between the valve element and the valve drive element will result in failure of the position sensor to adequately function. Consequently, the speed of the valve at the moment when it is seated on the valve seat is large enough for generating a large noise. Furthermore, it cannot be ensured that the valve is constantly moved to an accurate position for closing thereof.
Therefore, an object of the present invention is to overcome various problems encountered by the above-described known electro-magnetically operated valve, which is not exclusively, but preferably, used as intake and exhaust valves for internal combustion engines.
Another object of the present invention is to provide a novel apparatus for estimating a valve-clearance of an electro-magnetically operated valve defined as the spacing between a valve element and a valve drive element of the valve in order to achieve an accurate determining of a change in the valve position during the movement of the valve without assistance of any position sensor.
A further object of the present invention is to provide a controller for the operation of an electro-magnetically valve, which is able to achieve an optimum control of the valve by the use of dynamically estimated valve-clearance.
In accordance with one aspect of the present invention, there is provided a valve-clearance estimating apparatus for estimating a valve-clearance that is a minute spacing produced between a valve drive element and a valve element, which form part of a moving body of an electro-magnetically operated valve additionally provided with a pair of electromagnets arranged to be spaced apart from one another via the valve drive element and generating, upon being electrically excited, an electro-magnetic force acting on the valve drive element, and a pair of springs exhibiting a spring force also acting on the valve drive element, the electro-magnetic force and the spring force permitting the valve drive element to move thereby driving a movement of the valve element toward either one of valve-closing and valve-opening positions, wherein the valve-clearance estimating apparatus is operatively connected to a position sensor arranged to determine an instant position of the valve drive element of the electro-magnetically operated valve during a movement of the valve drive element, and includes: a mass-change estimating portion that estimates a change in a mass of the moving body moving together with the valve drive element; and a valve-clearance estimating portion that estimates the valve-clearance on the basis of the position of the valve drive element determined by the position sensor at a time when the change in the mass of the moving body is estimated.
In accordance with a further aspect of the present invention, there is provided a control apparatus for controlling the operation of an electro-magnetically operated valve including: a valve drive element; a valve element driven by the valve drive element; a pair of electro-magnets arranged to be spaced apart from one another via the valve drive element and generating, upon being electrically excited, an electro-magnetic force acting on the valve drive element; the valve drive element and the valve element forming an essential part of a moving body of the electro-magnetically operated valve, and a pair of springs exhibiting a spring force acting on the valve drive element, the electro-magnetic force and the spring force permitting the valve drive element to move thereby causing a movement of the valve element toward either one of valve-closing and valve-opening positions of the electro-magnetically operated valve. The control apparatus includes: an apparatus for estimating a valve-clearance that is a minute spacing produced between the valve drive element and the valve element, the valve-clearance estimating apparatus comprising a position sensor for determining a position of the valve drive element during a movement of the valve drive element, a mass-change estimating portion estimating a change in a mass of the moving body moving together with the valve drive element, and a valve-clearance estimating portion estimating the valve-clearance on the basis of the position of the valve drive element grasped by the position sensor at a time when the change in the mass of the moving body is estimated; and a control-switch arranged to switch a control gain in controlling the operation of the electro-magnetically operated valve in response to a position of the valve drive element determined by the position sensor of the valve-clearance estimating apparatus and a valve-clearance estimated by the valve-clearance estimating apparatus.
In accordance with a further aspect of the present invention, there is provided a method of controlling the operation of an electro-magnetically operated valve which is provided with: a valve drive element; a valve element driven by the valve drive element; a pair of electro-magnets arranged to be spaced apart from one another via the valve drive element and generating, upon being electrically excited, an electro-magnetic force acting on the valve drive element, the valve drive element and the valve element forming an essential part of a moving body of the electro-magnetically operated valve; a pair of springs exhibiting a spring force acting on the valve drive element, the electro-magnetic force and the spring force permitting the valve drive element to move thereby causing a movement of the valve element toward either one of valve-closing and valve-opening positions of the electro-magnetically operated valve; and an apparatus for estimating a valve-clearance that is a minute spacing produced between the valve drive element and the valve element, the valve-clearance estimating apparatus comprising a position sensor that determines an instant position of the valve drive element during a movement of the valve drive element, a mass-change estimating portion estimating a change in a mass of the moving body moving together with the valve drive element, and a valve-clearance estimating portion estimating the valve-clearance on the basis of the position of the valve drive element determined by the position sensor at a time when the change in the mass of the moving body is estimated, wherein the controlling method includes: switching a control gain in controlling the operation of the electro-magnetically operated valve in response to a position of the valve drive element grasped by the position sensor of the valve-clearance estimating apparatus and a valve-clearance estimated by the valve-clearance estimating apparatus.
The above and other objects, aspects, features and advantages of the present invention will become more apparent from the ensuing description of the preferred embodiments thereof, in conjunction the accompanying drawings.